Propeller pitch control



Dec. 1, 1953 IT. B. MARTIN 2,661,067

PROPELLER PITCH CONTROL Filed Feb. 1, 1944 4 Sheets-Sheet l 76 zoz J "I 75 zoa I8 I64 2 l8! M4 I INVENTOR THOMAS E. MART/N ATTORNEYS I80 D 1, 1953 T. B. MARTIN 2,661,067

PROPELLER PITCH CONTROL Filed Feb. 1, 1944 4 Sheets-Sheet 2 ATTORNEYS T. B. MARTIN PROPELLER FITCH CONTROL Dec. 1, 1953 4 Sheets-Sheet 3 Filed Feb. 1, 1 944 Dec. 1, 1953 T. B. MARTIN 2,561,067

PROPELLER FITCH CONTROL Filed Feb. 1, 1944 4 Sheets-Sheet Patented Dec. 1, 1953 UNITED STATES PATENT OFFICE PROPELLER PITCH CONTROL corporation of Delaware Application February 1, 1944, Serial No. 520,627

9 Claims.

This invention relates to controllable pitch propellers, and has for an object to provide them with means for feathering and unfeathering their blade pitch condition.

One additional object is to provide propeller mechanisms with means for feathering and unfeathering, both operations being selectively controlled at the will of the pilot, and not dependent upon rotation of the propeller, yet being itself contained and self-regenerative within the rotating unit.

Another object is to provide a hydraulic pitch control mechanism with a fluid circuit having sufficient reserve of potential in the form of an accumulator to effect both feathering and unfeathering of the blades without regeneration.

A further object of the invention is to provide selective control mechanism for feathering and unfeathering of the blades that normally will be passive during constant speed operation of the propeller but instantly available at will by means of a tripping mechanism for effecting the desired control of pitch change.

A further object of the invention is to provide a hydraulic system of control for feathering and unfeathering the pitch of propeller blades, which system includes a feathering valve unit and tripping mechanism that is selectively operable to provide a mechanical impulse for the purpose of initiating flow of fluid under pressure for both feathering and unfeathering operation.

A further object of the invention is to correlate constant speed control mechanism for a propeller pitch change mechanism and a feathering control, so that preselected movement of a control member will coincidentally set the control mechanism for theshift called for and connect therewith the source of potential operative to effect the selective extreme shift.

Anotherobject of the invention is to provide a hydraulic system of controlfor a constant speed propeller and selective control means for feathering and unfeathering the propeller to be effected by a trippable feathering valve control unit, inserted in the fluid circuit between the pressure developing means and a distributor valve unit with a relief branch safeguarding the system against damage from unwanted pressures.

Another object of the invention is to provide a hydraulically controlled constant speed propeller with means for feathering and 'unfeathering the blades, that enable construction and assembly complete :as a unit suitable for mounting on an available engine or propeller shaft without subsequent assembling in thezfield.

A further object of the invention is to provide a feathering propeller with feathering control units that are mountable and removable from the propeller structure without dismounting the propeller from its driving shaft.

A further object of the invention is to provide a feathering propeller with an accumulator and feathering control valve unit that may be re moved for repair or service without removing the propeller from the aircraft.

Yet another object of the invention is to provide a large capacity accumulator for a feather propeller that will not interfere with spinner support or with cannon fire through the axis of the propeller shaft.

Still another object of the invention is to provide a feathering propeller with an annular accumulator mounted concentric of the propeller shaft and for rotation with the propeller, and relatively immovable fluid connections with the fluid pressure system controlling the pitch of the blades.

Another object of the invention is to provide a self-contained hydraulic actuated constant speed controllable pitch propeller with feathering and unfeathering mechanism devoid of all external fluid connections, but having mechanical connection with a cockpit control whereby the speed level of constant speed control can be selected, and the feathering and unfeathering effected at will of the pilot.

Yet another object of the invention is to provide a feathering control for hydraulically actuated pitch shifting propellers that is embodied in a unit removable from the exterior of the regulator and provided with a fluid filter inserted in the pressure circuit of the system.

Another object is to provide an aircraft pro peller' capable of constant speed control by blade shift within a working range, and also capable of superposed control for blade shift to a range outside of the working range, with means operable at will to return the bladepitch to the Working range.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

Fig. l is a longitudinal sectional view of a feathering propeller mechanism involving the present invention, it being a view substantially as indicated by the line and arrows ll of Fig. 2. Fig.2 isa transverse sectional view through the regulator of the control mechanism substantially as indicated by the line and arrows 22 of Fig. 1.

Fig. 3 is a plan view of the trip mechanism and relief valve assembly substantially as indicated by the arrow 3 of Fig. 5.

Fig. 4 is a sectional view therethrough substantially as indicated by the line and arrows 44 of Fig. 3.

Fig. 5 is an enlarged fragmentary sectional view showing that portion of the fluid circuit from the accumulator to the control valve with its tripping mechanism.

Fig. 6 is a similar view of a modified form of the invention.

Fig. 7 is a schematic view illustrating the fluid circuit for the complete control of the propeller mechanism.

Fig. 8 is an enlarged transverse sectional view through the feathering control valve substantially as indicated by the line and arrows 88 of Fig.7.

Fig. 9 is an enlarged sectional view of the accumulator charging and feathering control valve unit detached from any supporting or connected structure.

Referring specifically to the drawings, I indicates an engine nosing or gear casing from which rotatably extends a propeller shaft I2 seating a rear cone I4, and by means of splines I6 driving a hub I8 where it is held by a front cone 20 and a shaft nut 22. The hub I3 provides radially extending sockets 24 within which are secured propeller blades 26 rotatable about pilot bearings 28 and within thrust bearings 30. There are a plurality of sockets and blades, and each blade 26 is hollowed out at its root to enclose a torque unit 32 consisting of a cylinder 34 drivingly connected to the blade and housing a piston 36 movable the length thereof and connected by spiral splines 38 with the cylinder and by other splines 40 with a hollow spindle 42 fixed to the blade bearing boss 44 supporting the pilot bearing 28. The piston is double acting, in that it divides the cylinder 34 into two collapsible or expansion chambers, one 46 at the outward end of the cylinder and the other 48 at the inward end of the cylinder. Fluid pressure applied to either end of the piston causes it to move along the cylinder and in so doing rotates the blade within its bearings. Equal and coincident rotation of all of the blades is assured by fitting each blade with a gear segment 49 that meshes with a master gear I mounted on antifriction bearings 53, the outer race 55 of which is secured in an enlarged bore 51 of the hub I8 in front of the bearing bosses 44. A thrust plate 59 secured to the forward end of the hub for keeping the bearing in place, has a. sleeved extension 6| whose end is disposed beneath the bosses 44 and is radially spaced about the nut 22. Thus, rotary motion transmitted to each of the blade gears 49 is also applied to the master gear 5I, which insures that no one blade will be shifted faster, or further than any of the other blades of the propeller. The application of fluid under pressure is controlled by a regulator 50 through tubular passages 52 and 54 One of which connects to a pipe 54a secured in the bearing boss and slidably extending through the piston 36.

The regulator 50 is shown chiefly in elevation in Fig. 2, and as indicated in Fig. 1, comprises an annular plate 56 joined with a cover shell 58 and an adapter assembly 60 to provide an annular chamber forming a reservoir 62 housing the propeller control apparatus and a quantity of fluid operating medium. The regulator so fashioned is secured on a rearwardly extending sleeve portion 64 of the hub I8 so as to be concentric with the shaft I2 and is there held by means of a sleeve nut 65 extending within the adapter 60 and threading onto the extension 64. The plate 56 embodies control passages 66 and 68 connecting with the tubular passages 52 and 54 respectively and also a pressure supply passage I0 extending from a pump or pressure creating device I2 to a juncture block "I3 for relief and certain control valve units, and also a feeder passage hi leading to a distributor valve station 76. Control passage 66 has a plurality of ports I8 each of which communicates with a tubular passage 52 leading to a chamber 46 of the torque unit so that all of the chambers 46 are exposed to the control passage 66, and the control passage 68 has a plurality of ports similarly connected to the tubular passages 54 and chambers 48.

At the station 76 there is located a governor valve unit 82 that embraces a porting sleeve 84 suitably mounted at the station and having a middle port 86 always open to the fluid in the passage 74, and axially spaced ports 88 and 90 opening to the control passages 66 and 68 respectively. The porting sleeve 84 is so mounted that its bore 92 is disposed radially of the axis of propeller rotation, and so that a valve plunger 94 fitted therein is capable of movement along the bore of the sleeve in response to domination of centrifugal force or spring force opposing it. The valve plunger 94 has a pair of spaced lands 98 and 98 which are positioned so as to cover the ports 88 and 90 respectively when the centrifugal force and spring force are in equilibrium, or are balanced. The valve plunger 94 is articulated at I06 with a lever I02 that extends substantially normally therefrom to rest upon a movable fulcrum I04 where it is maintained under the urge of a spring I06. The governor valve so constituted is adapted to effect constant speed operation of the propeller, whose speed level is determined by the position of the fulcrum I04 along the length of the lever I02 which determines the relation of the spring force and centrifugal force acting upon the valve plunger and its linkage.

Determination of the speed level of the control is made by movement of the fulcrum I04, which is supported by a carriage I08, toward and from the line of force exerted by the spring I06. Rigidly mounted on the plate or the governor valve unit there are guides IIO that extend along the length of the lever I02 and support the carriage I08 in sliding relation. An extension II2 of the carriage I08 extends into an annular groove II4 of a control ring I I6 which is disposed about and movable along the length of the adapter assembly 60. Rotation of the control ring is prevented by guide rods I I8 passing therethrough and anchored in the adapter-assembly which comprises a sleeve I20 extending across the reservoir 62 to engage bearings I22 and I24 in the members 56 and 58 along with sealing means that prevent leakage of fluid from the reservoir. Secured to the sleeve I20 and extending outside of the reservoir there is a guide ring I26 mounted on a pilot plate I28 and forming an annular channel within which there is oscillatably disposed a ring gear I30 with a lever I32 attached, which ring gear is in mesh with a plurality of pinions I34 carried by screw shafts I36 journalled in the sleeve I20 so as to thread into and out of the control ring I I6. The

memos? adapter assembly tending withthe pilot plate 128 has a journal hearing inthe regulator toy-reason of the bearings I22 and I24, but is restrained "from turning with the propeller mechanism by a lug or stop means I38 secured to the engine nose I and entering a slot or notch I40 of the pilot plate I28. Thus while the propeller isin operation the regulator Il'is rotated about the adapter assembly 60, and advantage is taken :of that to provide a toothed flange I42 on the sleeve I20 inside of the reservoir for engaging :a spurgear I44 of the pump I2, so that rotation of the propeller will also efiect rotation or driving of the pump I2.

As schematically shown in 'Fig. '7 of the drawings, driving of the pump I2 withdraws fluid from the reservoir '62 through the intake 14B and delivers it under pressure to the passages 10 and 74,

as will presently appear, by which it is delivered to the port '86 of the governor'valve unit. Assuming the propeller to be operating at some constant speed determined by the setting of the carriage and fulcrum I04, then the valve plunger 94 will'be in the equilibrum position and theilands "9'6 and 98 will cover bothoi the ports "88and 90,

creasing the pitch of the blade. At the same time the port 88 is opened to the end of the porting sleeve by which the opposite side of the piston 36 is relieved and drained to the reservoir 62. For a condition of underspeed, the spring I06 becomes the dominant force and the valve plunger M moves inward to uncover the port 38 to pressure of port 86, and the port =90 is opened to drain as shown in Fig. 7, and which conditions the piston 36 to rotate the blade to a reduced "pitch position.

In either instance the blade angle is quickly corrected to effect constant speed operation within the working range selected by positioning of the fulcrum I04.

Under operating conditions it sometimes 'becomes desirable or necessary to shift the blade pitch to an extreme position outsideof the normal or working range, and in-some instances continued rotation of the propeller cannot be relied upon to provide the necessary energy to accomplish that desired shift. That is especiallytrue when the propeller has been brought to rest for one reason or another. In order to have available :for use at those times a source of pressure that can be relied upon and used to move the blades to an extreme position, an accumulator I4! is mounted on the propeller with fluid connections I48 to the hydraulic system and a control valve I50 is provided by which the charge and discharge of the accumulator can be controlled.

The accumulator control valve mounts on the having a tubular extension I which extends through an opening in a diaphragm I69 where it is held by a retaining nut 'I 62 axially spaced from the diaphragm at -I63,-and forming a guide for Cooperating with the seat I54 there is a conic valve head I56 5 the passage of .a trip rod 164 'operable irom within the regulator. The diaphragm 13.0 is carried by a piston member 1266 that slides udthin Ithe chambered member I52 and is'under the urge 50f a spring 1 68 normally to close the portof the seat 4 54 by the valve head :I 56, and the diaphragm has a plurality of apertures I'IIl around the valve headsoas to subject both sides of the diaphragm to the same pressure. Obviously, the number of such apertures is not material and only one can be used if desired. The piston I68 has a tubular extension I12 centrally apertured at I74 to slide over a tubular boss N6 of a thrust head I'Ifl secured in theopen end of the chambered member 1-52 by a snap ring I80. In'the side walls of the tubular boss its there are valve ports I82 .controlled by the :aperturedportion I'M of the piston extension, and other ports 184 that openitrom the bore of boss to the outside end of the piston, while the end or the "boss is apertured at I85 :to "permit passage of the trip rod Hi4. S'eat'ed against the thrust head I18 there is a spool member 186 whose side wall is :apertured at I88 for passage of fluid, and which is so disposed as to seat one end of the spring 1'68 by which the spool is held against the thrust head I! I8, the periphery of the spoolmember being surrounded'bya screen or foraminous member I 90. 'The junction block :13 is apertured at 13.2, Figs. 5 and '7, for communication with the 'line Iii from the pressure source, and the skirt of the chambered'member 1'52 has slots at I94 to permit passage of fluid to the outside of the spool from where fluid flows through the screen and ports I88 and thence through the ports 182 and [84 to the bore of the 'boss and around the trip rod I64 along :an axial bore or passage 1960f the juncture block I3 to which is joined the passage i l. The thrust head I18 is socketed at I19 and there seats a 'seal'ring IBI adapted to engage over the end of a tubular boss I83 -as an-extension of the junction block '13 insuring that there is no direct cross how between the passages "it! and "I l as shown in Fig. '7, and thereby connects I96 directly with the bore of boss I15. The fluid under pump pressure also flows along'the rod I G l through the aperture atthe end of the tubular boss I76, through the retaining nut 2 to unseat a ball check valve I31 located in a fluted bore I93 of the valve head, and thence through an aperture I99 into the accumulator passage 8. The ball check valve I91 is adapted to be responsive to the pressure differential between the accumulator pressure and the pressure in the system so as to cause the valve to move longitudinally within the passage -I 98. :Pressure in excess of that permitted to pass to the accumulator It? builds up in the passage 4.95, Figs land "7, and exerts itself alonga groove 2% between the regulator plate 55 and a mounting block 252 for the trip mechanism toanenlarged bore 2% of an aperture receiving one oi. the screwdevices 2% for mounting the block on the plate, and .thence through .a passage .20.! to

v the interior of a pressure control valve 208. The

valve 203 has a plunger 269 with a land 2 II that normally prevents escape of fluid through apertures 'Z'Ili, by means of centrifugal force plus the pressure of a spring 2I2, but presenting an area exposed to the pressure of the line by which the exhaust ports may be opened.

The trip rod "it'd is slidable through the block 202 and has its inner end2 I 4 flattened as it passes through the guide I62 to engage the ball, and is also sufliciently smaller than the bore of the W- 'bular boss I16 which receives the rod to permit .the passage of fluid when the accumulator is being charged. The block 262 is slotted at 215 and into this slot the outer end of the rod I64 extends. A lever 2l6 which is supported on a pivot 258, as best shown in Figs. 6 and '7, has an arm 220 which extends into the slot 2H5 and engages rod [64, the arm normally resting against a stop pin 222. The lever 216 has a cam portion 224 at its free end that is engageable by a cross pin 226 mounted in and adapted to traverse the length of slots 228 which are provided by a carriage 230 having rollers 23! which are movable along guide ways 232 secured to the block 262 by screws 203. The carriage 230 has a depending extension or shoe 234 which engages the groove 1 I4 of the control ring l i6 which is moved to control the governor valve as heretofore described.

The accumulator I4! is of rigid wall construction and is mounted on the forward end of the propeller hub so as to be coaxially disposed there with and not disturb the balance of the entire assembly. Within the contemplation of the invention, the accumulator may take the form of an annular chamber such as shown in Figs. 1, 5, and 7, or it may take the form of an axially disposed cylinder of the form shown in Fig. 6, in either instance the accumulator being capable of assembly with the propeller hub before the propeller is mounted on the shaft, and assisting in the setting or withdrawing of the hub-shaft nut by which the propeller is secured on the shaft. In the annular type, per Fig. 1, the accumulator preserves the hollow characteristics of the shaft suitable for cannon fire and for passage of a sec ond shaft for a second propeller, as in a counterrotating structure. In either instance the accumulator or its mounting serves a secondary function in piloting a spinner for fairing the propeller structure.

Referring to the annular type of accumulator shown in Fig. 1, there are a pair of radially spaced cylindrical walls 240 and 242 each having a flange 244 and 246 respectively fitted with seal rings 24B engageable with the cylindrical wall of the other so as to form a fluid tight annular chamber adapted to enclose a rigid piston shell 252 at the inner edge of which adjacent wall 242 is a channel in which is a sealing ring 254, and on the outer surface of which is a channel which receives a sealing ring 256 slidably engaging the surfaces of the walls 242 and 246 respectively. The piston shell has a skirt 256 extending therefrom which is apertured at 263 into an annular groove 262 to reduce the metal to metal contact between the skirt and cylinder 240. Thereby, the concentric shells form a normally closed chamber that is divided by the piston into what may be termed a loading chamber 256, and a pressure chamber 25!, the flange 246 being fitted with a Schrader type air valve 264 by which the loading chamber may be pumped full of air to the desired pressure, while the cylinder 240 has a nipple 266 formed thereon to which the tube I46 may be secured by a clamp nut 268. The cylinders and piston member may be assembled as a unit in which position they are held by a spring ring 213 in the open end of the cylinder 24!) acting as a stop for the flange 246 of the inner cylinder 242. For mounting the accumulator the flange 244 is projected outwardly to form ears 272 through which extend some of the screws 274 by which the thrust plate 59 is secured to the end face of the hub E8. The flange 244 has an extension 216 which projects into the end of the sleeve extension 61 of the thrust plate 6 so that the accumulator is properly concentric with the axis of propeller rotation.

Received within the inner cylinder wall 242 of the accumulator there is a rotatable sleeve 2'53 that has castellations 260 which cooperate with the castellations of the nut 22 by which the latter may be turned from a point anterior to the accumulator, where the sleeve has slots 282 to receive a wrench. Against a shoulder 284 of the sleeve there bears a spring 235 that also engages a seating ring 286 abutting the flange 244 and the end of cylinder 242, which spring operates to keep the sleeve and nut in engaged relation. It is desirable to prevent relative rotation between the cylindrical members 243 and 242 so a cross pin 288 located in the flange 244 extends into a notch 296 of the cylinder 242 where it is kept from appreciable endwise displacement by the parts 6| and 218 as shown in Fig. 5. In that figure is also shown means for supporting the foreward end of the spinner and for locking the shaft nut against loosening. The spinner comprises a conic shell 292 whose base end is supported in any desired manner and terminates at its apex with a reinforcing ring 2% secured thereto by screws 296 under one of which there is a locking clip or plate 298 adapted to engage one of the slots 282.

In the form of mounting shown in Fig. 6, the accumulator is formed from a cylindrical wall 336 whose outer end is closed by a head 362 seating against a flange 334 of the cylinder, and sealed by a ring 386, the head member supporting the air valve 264 and threadedly receiving a rod or other member 368 for support of the spinner. The opposite end of the cylinder is notched at 310 to receive the castellations of the nut 22 and is of a diameter to slidably fit within the nut receiving bore of the hub beneath the bosses 44 where sealing rings 3|2 prevent fluid leakage, a snap ring 3 l 4 within the cylinder oper ating to retain an impervious head member 326 the periphery of which is sealed by ring 3l3. Within the cylinder 303 there is a piston 323 having a skirt 322 at each end of which there is a sealing ring 324 engageable with the inner surface of the cylinder. As in the earlier described device, the skirt 322 extends toward the loading chamber 250 and is engageable with the head or flange 302 so as to define the minimum volumetric content of the loading chamber. In both cases the pressure chamber 25l is practically collapsible as shown in full lines in Figs. 5 and 6 of the drawings, but upon increase of pressure is expandable to the extent of that delineated by the dot and dash line showing in the same figures. Here, the cylinder 366 provides an opening 326 from the pressure chamber 25! that opens into a passage 628 of the hub l8 and which leads to the control valve I53 as herein explained, in

this instance the passage 3'23 taking the place of the tube I48. Intermediate the length of the cylinder 300 there is an angled flange 3333 re ceivable by the bore 332 of a thrust ring 334 secured to the face of the hub and forming the outer race 336 of the bearing 53, there being a seal ring 338 for prevention of leakage, and

snap ring 340 that maintains the assembly in proper relation. The terminal end of the thrust ring 334 is notched at 342 for selective reception of a tang 344 on a locking ring 345 having on its inner periphery teeth 348 adapted to engage the notches of a toothed flange 350 on the cylinder 360. When the ring is in place a snap ring 352 secures the lock ring against dislodgement, Thus,

the. nut 22' is prevented from loosening... since it is. engaged by the end of the cylinder Meat 31%! and the cylinder is prevented from turning by the lock ring 346 engaging the notches 34-2" and the teeth of the flange 350. With the locking ring 346 disengaged, the cylinder can be rotated to tighten or loosen the shaft nut 22, by applying a wrench to the toothed. flange 35h.

In'eith'er form of construction the accumulator is formed byrigid wall members and their jointsaresealed against fluid leakage. That is done preferably by using soft or pliable rubber bands or rings lodged in grooves of such" dimension that assembly ofthe parts will effect some cormpression of the rubber to accomplish the seal. When the parts are assembled: they will be maintained in distendedrelation by the loading. pressure in. the chamber 258-, in such instance the pistons being moved to the extreme right hand of the views such. as to practically collapse the pressure chamber 25L To state-generally, and referring to Fig. 5, the accumulator provided for storing oil under pressure for feathering and unfeathering is shown bolted. to the front of the hub in place of the spinner adapter. It is an annular piston type or accumulator with the center hole large enoughto provide the same-size bore for the cannon as heretofore used. The outer shell is bolted to the hub' andthe inner shell is sealed to the delivery tube M8 is mounted by means of a flexible tube-connector as shown. This consists OfZa C-SECti'OIJ. rubber ring slipped-over the flaredend of the tube and held down with a screw cap. This cap is knurled and hasno wrench flats; It isto be tightened by hand only and safetied; to a nearby bolt. This connection is leakproof and? will maintain. its flexibility athigh. pressures. isfi-tted torthe forward end of the accumulator for preloading and is arranged toprotrude from the bolt circle at the nose of the: spinner for convenience and accessibility. Included in the accumulator assembly is. a. central sleeve received by the accumulator and arrangeol tohave driving connection. with the shaft. nut at. its inner end andto extendforward. of the accumulatorv at its outer end to receive the spinner" nose. Its outer end'is arranged with gwr'ench' slots so that the propeller may be installed on the airplane complete with spinner; thereby eliminating a majorperc'entage of the time re-' quir'ed.forinstallation; The nut is lockedby a locking p'latewhich engages the slots in"thesleeve end and" mounts under the" four fi-lli'ster headscrews on" the exterior of the spinner nose as shown. Eight equallyspaced holes are provided the locking plate so that the same indexing arrangement for lockingis provided as before; A -coil springsurrounding the sleeve maintains it;

against the shaft-nut to prevent chatter. In no case, however; could the sleeveslip r forward rar enoughtwdisengagethenut;

A high-pressure Schrader valve 254 ace-1,007

10 In operation the accumulator pistonii's mechanically stopped so that it takes a predetermined maximum volume of oil from the regulator and no' more. This definitely determines the maximum and minimum oil level in the regulator.

The. effect of changing temperatures on the preload pressure may then betaken as a change in maximum pressure or be distributed between pressure and volume asdesired by choosing the preload pressure accordingly.

The piston has another advantage in thatv it definitely divides the air and oil so that there is no question. as to their distribution in the cen" tri-fugalfield. Let it be assumed that the pistonwillclraw '75 cu. in. of oil. from the; regulator, and c8: cu. in. are'required to shift the blades from: the-low pitch stop to feather. remaining capacity for unfeathering back to 57 blade angle. This assumes the Worst conditions for feathering and no assistance from the pump. Thepump wijll assistsomewhat during feathering, andas soon as wind-milling isestablished on umfeathering' the pump will continue to decrease the blade pitch slowly. A large volume for preloading. is provided in the accumulator, and. the air preload pressure isabout 400 pounds per square inch with the accumulator empty.

As soon as the propelleris rotated the regulator supporting the pump is rotated about theadapter assembly by which the toothed-flangeMZ effects rotation of the pump gear IM developing. a fluid pressure within the pump 1-2, Figs. 2 and 7 That pressure iscommunicated through the-paw through the ports [8d to the interior of the hol-;.

low boss. The valve I54; I56 willthenbe closed and the ports I82 will: be restricted, so that the fluid under pressure'flows' through the opening. mg; in: the end of the tubular boss H6 around. the rod: l64-to the inside of the piston extensionl12 andthence'through the bore of theguidenut I62: andaround theflatteneot portion 2-H of the rod I64 to unseat the ball check valve i913 and thence through the passage i99 to the pressure ggigmber 251 by way of the tube its-or the passage member252- or 32 [tismoved away soas to increase. the compression of the gasor air the-loadingchamber 2 50; That continues until the" piston engagesthestop-between the end of its'skirt and the-headof thecylinder; Pressure developed inexcess of thatdefined-by the loading chamber is I also exerted-on. theother fluid. passages connected with. the: passage meof the' junction: block-=- E31. Thus, the pressure ot the line: will: effective: through thepassages leading; tothe governor valve uni-t -82 and: to the interior of: the pressure control valve 2H8. In the actual cmstru'cti'on: as shown: in Figs. 1 and 2-,. thepressurecontroh valve is disposed with: its: plunger 2'89 arranged along aradiusof rotation of the regul'atorso that centrifugal force acting; on. the plunger assists the spring; 2.12 in withdrawing the 13.1161 2! r front This leaves enough the accumulator is charged with fluid under pressure from. the pump 12:, the piston the ports 2I0, substantially as shown in Fig. '7. The line pressure in the passage 23": is applied to the full area of the land 2 I I, and when it develops to the point of overcoming centrifugal force and force of the spring 2 I2 applied to the plunger, it moves the plunger to a position to open the ports 2H], which immediately relieves the pressure in the line and spills some of the fluid medium back into the reservoir 82. Thus, the pressure control valve 268 variably controls the maximum of pres sure that may be carried in the system since the valve 208 responds to two'variable forces opposing each other, one being centrifugal force and spring force applied to the plunger 239 moving it outward, and the other being pressure in the system applied to the area of 2H moving the plunger 2&9 inward. With the propeller mechanism rotating at high on-speed, the centrifugal force exerted on the plunger 2539 and assisted by the spring in will permit a maximum pressure to exist in the fluid pressure system, the pressure of the system always present at the end area of land 2II in opposition to the centrifugal and spring forces, tends to open the ports 2%, upon approach to the maximum pressure. With the propeller operating at a low on-speed, the centrifugal force acting upon the valve member zee would be less, wherefore the combined effects of spring force and centrifugal force opposing the pressure upon the end area of land 2 would be lower and permit the opening of ports 2H1 at a lower system pressure than for a fast rotating propeller. The maximum pressure limit may be selected by calibration of the spring 2 I2, the mass of plunger 209, the area of land 2H, and the radial location of the valve unit on the plate 56, and the maximum pressure limit chosen will depend upon the needs of the propeller mechanism to be served. A small two bladed propeller will not need as high an operating pressure, nor will it require as large a flow of fluid as a large four bladed propeller, the determining factor being that the system will always carry sufiicient fluid pressure to actuate the torque units whenever the governor valve 82 moves to open one of the control ports.

During this cycle of operation the feathering control valve will be in the condition illustrated in Figs. 5 and 9, with the piston 252 in the illustrated dot and dash line position. To make available the pressure of the accumulator for feathering the blades 25, the lever E32 (Fig. 1) is oscillated so as to move the control ring i It forward along the sleeve I23 to effect the position shown in Fig. 5, which moves the carriage 238 to a position against the regulator plate 56. That movement of the carriage first upsets the equilibrium of the governor valve 82 so that the valve plunger 94 is now in an outward position (downward instead of upward, as shown in Fig. '7) connecting the pressure supply port 85 to the increase pitch port 90 without any restriction due to partial covering of the port 90 by the land 98. The piston chamber at then being connected directly with the passage it immediately reduces the pressure of the system to a lowvalue, since the governor is now nonoperative to correct for loss of speed. Also the pressure in the system supplied by the decreasing rotation of the pump effects increased pitch shift of the blades which rapidly reduce the speed of rotation and a decided loss of pressure potential in the system up to the backside of the piston extension I12 and around the spring I653. The second event incident to movement of the carriage carries the cross pin 22% beneath the.

cam 224 of the lever 2I5 whose arm 229 depresses the trip rod I64 which upon being moved inward of the valve unit upsets the ball check valve I91, allowing a spurt of pressure fluid from the accumulator through the port I99 and the guide nut I62 to the inside of the piston extension I'IZ. From there the pressure of the accumulator is exerted on the full area of the piston 56 5 against the low pressure around the extension H2 which causes the piston to move in compressing the spring I68. That movement of the piston uncovers the ports I82 and also withdraws the conic valve I56 from its seat Hi l substantially as shown in Fig. '7. The direct effect of the accumulator pressure is immediately and greatly increased from the area of the port let to the full area of the piston I66, which for the time being withholds the valve I56 from reseating. The fluid in the accumulator under high pressure then flows through the port I54, the apertures no of the diaphragm and inside of the piston extension, then through the ports I82 and passages I96 and "I' l to the governing valve unit 82 where it is manifest at the port 86 as shown in Fig. '7.

At the same time that the carriage 23 i is moved against the regulator plate 56, the carriage I98 for the governor valve unit will also be moved to a position such that the fulcrum IM will be between the spring IIlB and the valve plunger 94, causing the plunger to be moved radially outward as indicated by the dotted line position shown in Fig. '7. That as has been stated will connect the control passage 54, 68 and port as with the pressure supply port 86 so that the pressure of the line will be exerted in the chamber 38 of the torque unit for movement of the blade to the feathered position, the chamber 48 of the torque unit relieving itself by fluid flow through Ma, 52, 66, 88 and $2 in returning to the reservoir 62. As soon as the feathering position is reached the pressure differential on the piston I65 is eliminated and the spring 268 effects reclosing of the valve I54, 56 substantially as shown in Fig. 5. The capacity and design of the accumulator is such that only a portion of its potential will be used in effecting the feathered movement of the blades.

To unfeather the blades, the cockpit control is manipulated to effect oscillation of the lever I32 for moving the control ring lit to the aft end of the adapter sleeve, such as shown in full lines in Fig. '7, where it appears that both carriages I98 and 239 have been moved to the right. That movement of the carriage I98 conditions the governor valve unit 82 for connecting the pressure supply port 86 with the pitch decrease port 88. That movement of the carriage 235 effects another cammed movement of the lever 2H5 which again moves the trip rod I65 to repeat the described operation of the feathering control valve. However, in this instance the governor valve unit connects the pressure source with the pitch decreasing side of the torque unit instead of with the pitch increase side, and the pressure of the accumulator is then available to shift the blades into the working position, or sufficiently that windmilling of the propeller will be effected and may be sufficient to crank the motor for restarting. Thus, the propeller may be feathered and unfeathered at will while in flight, or even while the plane is standing still on the field or in the hangar, It is not necessary that the engine be running when either feathering or unf eathering is accomplished, for the accumulator, once it is geese l3 c arged, re ains its eateries iiritil the the this is maniia'matd. I v w To sum 'a-rize operation or the control valve I50, and referring to" the section of the regulator shown in Figs. 5 and 7 there-is shown a tripping mechanism inside the real st-er and an eiternally removable v alve and filter assembly m ne with it on the out dle or the fo'rw d wall. The purpose r thetr'ipping iiieeria ,t name a me; chanic al iinpiils'e to the valve the purpose 'of initiating now from the accu H ator both for feathering and unfeath nn is is done by provid ng a carriage s'lidably e'riteaeii rollers and arj yinga shoe which engages he genteel in the same manner as the governs? shoe. The rails t the carriage are slotted. to Carfii a roller bet efi them as shee at 225 fai'nd223. This roller can slide sack aria fern; about as inch. The carnage is Shawn in the reatnera steam in Fig. 5'. Assume that inov'ed sea; to the other end of'its save and then mated to it's priestess snows. Nause win easements the ro ler 226 is engaged by the 224 er ten crank 2 20 The bell crane will then be rotated about its pivot 2 I 8 and its seen arm will push the rod I64. When the roller passes the apex of the cani it will move out from utdemtana along its slot, releasing th bell which theaarops bagr gamst metal 222. At the same time the governor 8 2 in answer location in the regulator has been shirted by thl control ring I I 6 into positive high piteh position which directs t e blades tofeather upon application of hydraulicpressure.- re unfather theblad'es the control ring 4 will move thecai'i iage in the opposite direction until the roller ggfi has reached the other end es its slot 228 whereupon it will be "forced past the cam 2 24 againandwill repeat-the o erates of pushing and releasing the rod I55. this time the governor will be movedbjthe control r nginto its decrease pitch position thereby directing the blades to unfeather upon application of hydraulic pressure. The lost motion or therouer Z6 its s t 228 sqs ves Pieve'i e d ie tripping of the rod I64 if the control ring should r t iehi v d t v t n e oth d b ances while the propeller is in feathered 'coiidi-- tion.

1 1 we i i b aun e 6f ic l s ur du in a i e err es ihe i 9f v ve is qyidedii 2 desi fI emq a efi i r. n 0: ederer s f i t accumulatorenters at the forward end of the cap and is normally seale'd by the valve hu ger I56 an the check ball I31. Pressure oil train the pump 12 enters the cavity in the regulator hous ins, h n t e r ds ei hold. t e rf lh Q 1,., i eq d hro m 1 t 9.4 in he hnerj d i h we n f esh its net screen I 90. It then flowstoward the center of the cap ;a ,lfl 'd t1"1l' 0u gh the holes I84 into the center tube. From there it flows into the -regulator easing where it is directed to thegovernor 82 and eih r' e sur e l 6.29 hrq e QPPYO' Prise Passee nt b ypfth ring n a *E -Q iW. hi h a 73, t as q- Th nrovieesn r e ump Wi W eed see ati fihesqv r F idi q th m canalso pass into the outer end of the cap at ial: and if the pump pressure exceeds the pressure in the accumulator itwill move the checleball and pass on into the accumulator fg nfilliruz. The 168 holds the plunger paee miy on it" seat I 54 against accumulator pressures up to sheet 1200 p. s. 1. Above this pressure it acts as a reiiei vaite against pressure increases than may result from rising t mperatures-u; for iil-' stance, the airplane is left standing in the with the accumulator full. I

When it is desired to feather the propeller the control ring I I6 is moved to extreme feather pose tion and three things happen at once mega: ernor a2 is shifted to positive high pitch pus-inert, the pressure to the governor drops irorn that established 'by the pressureeojntroi va e 208 to that required toinove the blades, and the 'cjh'ecle ball I9? receives animpulse from the rod its and passes a shot of oil from theaccumulator into the space behind it. This shot of oil again raises the ressure in its immediate vicinity and acting an the larger area of the piston I 65 causes it to move against the spring I68, The plunge'r I55 also moves back allowing a fioo'd of oil to rush from the accumulator against the piston I66. Piston I66 moves away and uncovers the holes :84 allowing the accumulated flow to enter the regulator and new to the governor. when the blades reach the feathered position the fic'lw of oil to the torque unit's ceases and pressures are equalized throughout the system. There is no longer a pressure drop through the holes I 84 and the spring I68 is then able to move the piston I66 back until theplun'ger use again seats use-1i The pressure in the system may then leak off without further drain from the accumulator.

When it is desired to unfeath'er the propeller the control ring is moved in the opposite direc'-' tion to a position shown in Fig. '7 and the above series of events is repeated, the onlv difference being that the governor 82 is thereby moved to its decrease pitch position and the blades turn in the opposite direction.

While the embodiment of the present invention as herein disclosed, constitutes a preferred term, it is to be understoodthat other forms might be adopted, all coming within the scope of the claims which follow. 7 7

What is claimed is as follows.

'1. Acontrollable pitch propeller uni-t corn-prising', a hollow shaft, a propeller hub mounted on the shaft and having radially extending blade sockets, blades each having a fluid niotor mount;- ed for rotation in the sockets, a fluid operated regulator including a fluid charged reservoir, a pump operable upon rotation of the propeller and a governor valve for supplying fluid under pressure to actuate the blade motors, said regulator being mounted on the hub in the rear oi the blade sockets, an annular accumulator mounted on the hub in front of the socl zets conduit means connecting the accumulator with the pump and governor valve and including a selectively operable control valve for admitting fluid stored in the accumulator to the blade meters, a tubular extension aligned with the hollow shaft and extending axially within the annularaccumulator, a nut for securing said propeller Hub to the hollow shaft, means on saidextension 'hgaging said nut and e'fiective to adjust thefriut upon'movement of said e'x't'efi'sio'n, and for locking said extension in adjusted 'pbsi so as to hold the hubretaihlhg hut in position and prevent loosening thereof. ,v

A controllable pitch propeller having blades adjustable about their axes, reversible "fluid inotive means for actuating the blades through two adjoining ranges or blade inclination, the "or tem for the fluid motive means, speed responsive means for controlling the blade angle through the working range, an accumulator in communication with the fluid pressure system, a differential pressure responsive valve interposed in said fluid pressure system for connecting the accumulator to said system, said valve including a movable means responsive to and operated by the pressure of the fluid in the fluid pressure system for controlling the charging of the accumulator, means for operating said valve to effect communication between the accumulator and said fluid motive means so as to communicate the pressure of the accumulator to said fluid motive means, means for controlling the operation of the speed responsive means and adapted to be operatively connected to said valve operating means to effect operation of the valve operating means to control the communication of fluid pressure from the accumulator to said fluid motive means in order that the blade pitch may be shifted as desired from one pitch range to the other.

3. A propeller unit having pitch shiftable blades, blade motors, and a hydraulic regulator for adjusting the blades to a selectable rota-tive speed for an aircraft, comprising in combination, a self-contained fluid pressure system within the propeller unit, speed responsive means for altering the blade pitch between a maximum and a minimum blade angle, manual means for operation of said speed responsive means for selecting the rotative speed of operation, a rigid walled cylinder, a rigid piston within the cylinder dividing it into a preloading chamber and a pressure chamber, a fluid connection between the pressure chamber and said system, a valve unit interposed in the fluid connection between the pressure chamber and system and movable by the fluid in the fluid pressure system to a position to admit fluid under pressure from the system to the pressure chamber of said cylinder whereby the preloading chamber is compressed and fluid under pressure is stored in said pressure chamber, a trip rod operable upon the valve for moving said valve to a position to efiect communication between said pressure chamber and the fluid pressure system so as to communicate the pressure of said chamber to the fluid pressure system independent of propeller rotation in order to effect feathering or unfeathering of the propeller, and means including a part of said manual means for effecting movement of said trip rod.

4. In a controllable pitch aircraft propeller having shiftable blades and fluid pressure actuated means for shifting the blade angle between high and low pitch limits of a working range and a self-contained fluid pressure developing means with a pressure line for supplying fluid under pressure to said fluid pressure actuated means, the combination of means for selectively shifting the blades to an angle outside of the working range and for returning the blades to an angle within the working range, including a rigid walled accumulator mounted on the propeller, means connecting the accumulator and pressure line including a valve unit having a check valve permitting fluid flow from the line into the accumulator, a spring pressed piston and valve head supporting the check valve and normally closing a port against return flow from the accumulator, a trip rod for upsetting the check valve and for admitting the full force of the accumulator pressure to the piston for withdrawing the valve head whereby the fluid pressure of the accumulator is exerted on the pressure line, and means for id actuating the trip rod and for coincidentally connecting one side of the pressure actuated means with the pressure line, whereby extreme shift of the blades will be effected upon upsetting of the said check valve.

5. In a controllable pitch aircraft propeller having shiftable blades and hydraudically actuated means for altering the pitch angle of the propeller blades, the combination comprising, a fluid pressure regulator rotatable with the propeller and having a distributor valve adapted to control the application of fluid under pressure to the pitch angle altering means, a source of fluid pressure, an accumulator rotatable with the propeller, conduit means connecting the accumulator with the fluid pressure source in advance of the distributor valve, and a control valve in the conduit means normally eflecting charge of the accumulator with fluid under pressure from the source, and for selectively exposing the charge of the accumulator to the distributor valve and thence to the hydraulically actuated means, said control valve including a high pressure flow valve, a check valve carried by the flow valve, a piston and springnormally urging the flow valve to a closed position but adapted to back off on exertion of fluid pressure from the accumulator above a predetermined maximum pressure, means for interrupting the control by the distributor valve and for coincidentally unseating the check valve for exposing the piston to the fluid pressure of the accumulator for selectively opening the flow valve, and valve means actuated by the retraction of the piston for applying the full force of the fluid pressure of the accumulator through the distributor valve and to the hy draulically actuated means for shifting the pitch angle of the blades.

6. In a controllable pitch propeller for aircraft, having pitch shiftable blades and fluid pressure actuated means for altering the pitch angle of the blades, and a hollow shaft for mounting the propeller, th combination comprising, an annular regulator mechanism surrounding the shaft and rotatable with the propeller, a pump driven by the regulator to develop a source of liquid pressure and apply the fluid pressure developed to the fluid pressure actuated means, an accumulator also rotatable with the propeller, conduit means including a control valve unit connecting the accumulator with the source of fluid pressure, said accumulator comprising a pair of rigid telescoping shells of annular form entirely clear and unobstructed at their centers to preserve clearance for cannon fire through said hollow shaft, a rigid piston movable between the telescoping shells for dividing the enclosure into a fluid pressure chamber and a preloading chamber, said piston having a skirt defining the minimum volumetric content of the preloading chamber, and means for mounting the a c-cumulator on the propeller concentric with the axis of the propeller shaft.

'7. A controllable pitch propeller having blades adjustable about their axes, reversible fluid motive means for actuating the blades through two adjoining ranges of blade inclination, one of which ranges is for normal constant speed operation, and the other of which is for supplemental blade pitch control, a fluid pressure system for the fluid motive means, speed responsive means for controlling the blade angle through the working range, an accumulator in communication with the fluid pressure system, a flow sensitive valve exposed to the pressure in the system for charging 17 the accumulator, trip means operable upon the flow sensitive valve for exposing the fluid motive means to the pressure of the accumulator, means operable upon the flow sensitive valve when the fluid pressure upon the fluid motive means equals the pressure in the accumulator for closing the accumulator to retain fluid pressure therein against leakage and for a subsequent and reverse application to said fluid motive means, and means operable upon the speed responsive means and upon the trip means for selecting the exposure of the fluid motive means to the accumulator, whereby the blade pitch may be shifted at will into either range from the other range.

8. In a controllable pitch propeller having pitch shiftable blades and a fluid operated system of control with blade motors for altering the blade angle, the combination of means for feathering the blades comprising, a pressure source developed by rotation of the propeller, a cylinder mounted on the hub in front of the blades, a rigid piston traversing the length of the cylinder and dividing it into a preloading chamber and a pressure chamber, passage means connecting the pressure chamher with the fluid operated system, a valve unit inserted into the passage means and operable to admit fluid to the pressure chamber upon rotation of the propeller, and means including a flow valve selectively operable for opening the full charge of the pressure chamber to the fluid operated system whether or not the propeller is rotating.

9. In' a constant speed controllable pitch propeller having fluid pressure operated mechanism for adjusting the blade pitch within a working range and a regulator for supplying fluid under controlled pressure to the fluid pressure operated mechanism, the combination of a reservoir in the regulator providing a supply of fluid, pump means for applying the fluid under pressure to the pressure operated mechanism, manually controlled means for selecting the speed level for which the constant speed control will be efiected and for shifting the blade pitch to an extreme position outside of the Working range, an accumulator having a pressure chamber preloaded against self-expansion, means connecting the pressure chamber with the reservoir and the pressure operated mechanism and under control of said manually controlled means, said connecting means in cluding a valve unit removably mounted on the regulator, and including a spring pressed piston normally stopping return flow from the pressure chamber, a check valve carried by the piston, and a trip rod selectively operable by the manually controlled means for upsetting the check valve, whereby the force of the pressure chamber is then operable upon the piston to compress the spring and allow return flow of pressure fluid from the pressure chamber to the fluid pressure operated mechanism coincident with shifting of the manually controlled means to an extreme position.

THOMAS B. MARTIN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,216,416 Mader Oct. 1, 1940 2,243,852 Caldwell June 3, 1941 2,257,126 Rindfleisch Sept. 30, 1941 2,296,288 Martin Sept. 22, 1942 2,307,102 Blanchard et al Jan. 5, 1943 2,308,223 Matteucci Jan. 12, 1943 2,333,973 Beebe Nov. 9, 1943 2,391,699 Haines et a1 Dec. 25, 1945 FOREIGN PATENTS Number Country Date 113,329 Australia July 3, 1941 703,319 Germany Feb. 6, 1941 

